The present invention is an improvement over my earlier prior patent. U.S. Pat. No. 5,503,655 of Apr. 2, 1995, the disclosure of which is incorporated herein by reference. In this earlier patent, there is described a process in which a liquid slag containing titanium dioxide is reduced to a mixture of titanium dioxide and iron, the latter separated out to produce about 95% pure titanium dioxide, the balance being impurities. In subsequent processing, the partially pure titanium dioxide is melted and processed to remove any residual iron and other impurities to form titanium dioxide powder. If titanium metal or an alloy of titanium is to be formed, the titanium oxide powder is heated in a vacuum to remove the oxygen, forming high purity titanium metal which can then be alloyed.
Numerous other disclosures for processing and making titanium alloys are present in the art. Descriptions of some of these are found in the below listed patents:
______________________________________ U.S. Pat. No. 4793854 U.S. Pat. No. 3237254 U.S. Pat. No. 3549353 U.S. Pat. No. 3494804 U.S. Pat. No. 4828608 U.S. Pat. No. 4027722 U.S. Pat. No. 3546348 U.S. Pat. No. 2997760 U.S. Pat. No. 3210454 U.S. Pat. No. 3343828 U.S. Pat. No. 4035574 U.S. Pat. No. 4838340 U.S. Pat. No. 3467167 U.S. Pat. No. 2727937 U.S. Pat. No. 3342250 U.S. Pat. No. 4488902 U.S. Pat. No. 3764297 British Pat. No. 809444 U.S. Pat. No. 3607222 Canadian Pat. No. 549299 ______________________________________
It is known that titanium, especially some of its alloys, e.g., titanium-aluminum-vanadium alloys such as Ti.sub.6 Al.sub.4 V are important because they are ideally suited for a wide variety of applications in the aerospace, aircraft, military, and automotive fields. Titanium and its alloys, including that mentioned, combine the attractive properties of high strength and light weight with resistance to corrosion and stability under high temperatures. For example, titanium is very strong but only about 60% as dense as iron and parts made of titanium will weigh only 60% as much as the same part made of steel. While titanium is relatively easy to fabricate, there are numerous impediments to its widespread use. Refining titanium is energy intensive and involves significant costs in handling due to the need for toxic chemicals for its refining. Furthermore, in refining titanium, there is a high cost involved in disposing of the toxic byproducts produced in the refinery process. Finally there are the geopolitical aspects of having to obtain most of the semi-processed titanium sponge from former communist and communist countries as well as from the Republic of South Africa.
It is also known to process rutile, the latter basically a titanium oxide ore, by chlorinating the titanium dioxide ore in the presence of chlorine gas and carbon resulting in the formation of titanium tetrachloride and carbon dioxide. The titanium chloride is then processed by distillation in the presence of magnesium to produce titanium metal and magnesium chloride. The difficulty with this process is that magnesium metal is a very expensive reducing agent typically made by precipitating the magnesium as a hydroxide from sea water, the hydroxide being converted to the chloride by hydrochloric acid. The water is then evaporated and the magnesium chloride melted and electrolyzed with magnesium metal produced at the cathode and chlorine produced at the anode. It is apparent that such processing may involve potentially environmentally hazardous materials and byproducts.
Thus, it is a primary object of this invention to provide an improved and cost effective process for the production of high purity titanium and its alloys from a starting ore containing titanium and preferably in an oxide form.
Another object of the present invention is the conversion of a titanium bearing ore such as rutile or illmentite to an essentially pure titanium tetrachloride followed by reduction to titanium which is then followed by refining of the titanium to a pure state and optionally alloying the same.
Another object of this invention is the provision of an improved process for the production of a high purity titanium-aluminum-vanadium alloy such as Ti.sub.6 AL.sub.4 V.
Another object of this invention is to process molten titanium under conditions which prevent contact with environmental air which is of changing composition and processing the molten metal under at least two vacuum phases to outgas the metal and optionally to produce a titanium-aluminum-vanadium alloy.
These objects and features of the present invention will become more apparent form the following detailed description which provides detailed information regarding both the process and apparatus and which is for purposes of illustration and should not be construed as a limitation on the present invention.